1. Field of the Invention
This invention relates to a condenser provided with forced cooling means and more particularly to a condenser provided with forced cooling means capable of enhancing the operational ability of a condenser incorporated in an air conditioner for an automobile without entailing a dimensional increase of the condenser.
2. Description of the Prior Art
Generally, while an automobile is in a parked state, the temperature inside its coach is elevated to a fairly high level by the radiant heat. At the time that the automobile is started, therefore, the internal temperature of the coach is desired to be quickly lowered (hereinafter referred to as "cooling-down") by setting an air conditioner in the automobile into operation. During the process of this cooling-down, the air conditioner is operating at its maximum capacity. When this cooling-down is quick, the thermal load resulting from the accumulation of radiant heat is quickly decreased, the internal heat of the coach is quickly returned to the basic level of thermal load, and the air conditioner is consequently allowed not only to manifest its stable cooling ability but also relieve itself of the noise attendant on the full-speed operation of a fan during the cooling-down. From this point of view, the desirability of improving the maximum cooling ability of an automobile air conditioner for the enhancement of the cooling-down ability has been finding enthusiastic recognition recently.
For the improvement of the maximum cooling ability of an air conditioner, an idea of enlarging various component devices of a refrigeration cycle in the air conditioner as by increasing heat-transfer areas of heat exchangers such as condensers and giving an increased capacity to a compressor, for example, may be conceived. This enlargement of various devices, however, not only has its limit by reason of space but also entails an increase in the amount of a coolant and an addition to the weight of the automobile and a decrease in fuel economy. These outcomes of the enlargement are directly contrary to the current worldwide trend of automobiles toward decreasing component devices in volume and weight and improving fuel economy.
As respects condensers, for example, among the condensers invented to date for use in automobile air conditioners are those of the serpentine type having a flat profile tube provided therein with a plurality of flow paths and bent serpentinely and, therefore, allowing a coolant to flow along the profile tube and those of the type having a multiplicity of flat tubes laid to intercommunicate a pair of parallelly disposed header tanks and consequently giving rise to a multiplicity of parallel flows of a coolant (hereinafter referred to as "multi-flow type"). The condensers of the multi-flow type, as compared with those of the serpentine type, have the advantages of allowing a decrease in the wall thickness of tube, offering a small resistance to the flow of a coolant, and generally exhibiting a high heat-exchange ability. They nevertheless suffer from the disadvantage of the header tanks and their vicinities permitting virtually no flow of cooling air, producing virtually no heat-exchange action, and making no contribution to the ability of the condenser and proving only wasteful. Particularly when the header tank on the coolant inlet side which is destined to introduce the coolant in a heated state fails to perform exchange of heat efficiently within itself and in its vicinity, the condensers are inevitably required to secure their prescribed condensing ability by elongating the flat tubes serving as parts for exchanging heat with air or increasing the number of such flat tubes and consequently opening up the possibility of enlarging the relevant devices. Thus, in the condensers which rely solely on air cooling, it is extremely difficult to improve the condensing ability without enlarging the relevant devices.
A technique of improving the ability of a condenser while avoiding enlargement of devices has been materialized, for example, by a process which comprises spraying atomized water onto the surface of the condenser and consequently allowing the atomized water impinging on the surface to be vaporized by the heat of the condenser. Indeed the supplemental incorporation in a condenser of the system of vaporizing water and, at the same time, liquefying a gaseous coolant may be effective in improving not merely a condenser of the multi-flow type but also a condenser of the serpentine type, the technique under discussion which resides exclusively in spraying atomized water onto the surface of a condenser has the possibility that the exchange of heat between the water and the gaseous coolant inside the condenser will not proceed sufficiently in proportion to the amount of the water to be sprayed. Moreover, since the system is not in a hermetically closed state, the pressure thereof cannot be adjusted relative to the water and the utilization of the latent heat resulting from the vaporization of water has its limit. This technique, therefore, cannot be expected to effect a very conspicuous improvement in the ability of the condenser because the efficiency with which the heat is exchanged between the water and the gaseous coolant never deserves to be held in high esteem. Further, since the water is sprayed in an atomized state onto the surface of the condenser, there is the possibility of the water corroding the condenser.
For the purpose of avoiding these problems, therefore, techniques of water-cooling the gaseous coolant have been invented as disclosed in Japanese Utility Model Publication SHO 57(1982)-58,546 and U.S. Pat. No. 4,676,071.